1. Field of the Invention
The present invention is directed to devices and methods to transfer power wirelessly to other devices and, more particularly, to such devices and methods that are capable of being self-powered, for example, by one or more batteries.
2. Background of the Invention
Wireless power transmission, such as, by magnetic coil induction, is used in a variety of applications to charge products including, but not limited to, electric-powered transportation carts, power tools, and cooking appliances. Wireless power chargers for mobile devices have also recently entered the market. In one example, these chargers use a charging mat that must be plugged into an electrical wall socket to transmit power wirelessly. Generally, the mobile device, such as, a cell phone or smart phone, is provided with a separate cover and battery connector, in addition to the usual device structures. When charging is to be undertaken, the separate cover is coupled to the battery via the battery connector. The user thereafter places the device onto the charging mat and the mat is energized. When the device is placed in the proper location on the charging mat, a receiver in the cover receives the wirelessly transmitted power and the power is delivered to the device battery through the battery connector to charge the mobile device.
Various drawbacks have been identified with prior wireless power chargers. For example, such chargers lack portability because they are generally large and bulky and are not easily placed in a user's pocket, purse, briefcase, etc. Further, such chargers require a connection to an external power source, e.g., a connection to an A/C power source from an electrical wall or car outlet. This requirement has obvious drawbacks since an external power source is not always available when needed or desired, especially in today's mobile society. Chargers that require a connection to an external power source are also energy inefficient because they typically draw power from the external power source at all times even when a device is not being charged.
Further, the use of a separate cover and battery connector to charge a device may be considered undesirable because of the need to remove any existing cover from the device and replace the cover with the separate cover and battery connector, which, in many cases, does not adequately protect the mobile device if the device is dropped.